Hydraulic pump motor

ABSTRACT

A positive displacement hydraulic pump (motor) which employs a gerotor gear set for displacing (for being displaced by) the fluid. The gear set includes an externally toothed rotor and an internally toothed stator ring. The teeth of the stator ring comprise roller vanes for meshing with the teeth of the stator. The capacity of the pump can be varied, in one embodiment by varying the degree of overlapping of the teeth of the rotor and stator ring and thus varying the effective displacement of the gears, and in another embodiment by employing a second gerotor gear set, the phase of which can be adjusted with respect to the first gerotor gear set for varying the effective displacement of both sets.

United States Patent White, Jr. et al.

[ Aug. 29, 1972 [54] HYDRAULIC PUMP MOTOR [72] Inventors: Hollis N. White, Jr., Lafayette; Dale E. Bough, West Lafayette, both of 21 Appl. No.: 69,580

[52] US. Cl ..418/21, 418/61 [51] Int. Cl ..F01c 21/16, F04c 15/04, F03c 3/00 [58] Field ofSearch ..418/2l,61,225

[56] References Cited UNITED STATES PATENTS 2,484,789 10/1949 Hill et al. ..418/21 3,460,481 8/1969 White, Jr ..418/61 1,990,750 2/1935 Pigott ..418/21 FOREIGN PATENTS OR APPLICATIONS 203,745 2/ 1923 Great Britain ..418/2l Great Britain ..4l8/2l Switzerland ..418/21 Primary Examiner-Carlton R, Croyle Assistant Examiner-Richard J. Sher Att0meyl-lill, Sherman, Meroni, Gross & Simpson [57] ABSTRACT A positive displacement hydraulic pump (motor) which employs a gerotor gear set for displacing (for being displaced by) the fluid. The gear set includes an externally toothed rotor and an internally toothed stator ring. The teeth of the stator ring comprise roller vanes for meshing with the teeth of the stator. The capacity of the pump can be varied, in one embodiment by varying the degree of overlapping of the teeth of the rotor and stator ring and thus varying the effective displacement of the gears, and in another embodiment by employing a second gerotor gear set, the phase of which can be adjusted with respect to the first gerotor gear set for varying the effective displacement of both sets.

2 Claims, 13 Drawing Figures PAIENTEmuszs I972 3,687 57 sum 3 or s INVENTORS H m/5 /V. M4176, JR; D445 4?. m/6% PATENIEDA B m2 3.687578 SHEET '4 0f 5 D426 5. Sway P'A'TENTEDmsze I972 3.687.578

sum 5 or 5 il! HUM.

I N VEN TOR 5 14041.15 A! 71 4/75, JR.

D44: .5. 5,0uw/

BY%%% 6 ATTORNEYS HYDRAULIC PUMP MOTOR BACKGROUND OF THE INVENTION This invention relates generally to the field of positive displacement hydraulic pumps or motors and more particularly to such pumps or motors which employ gerotor gear members for displacing or being displaced by the fluid.

Gerotor gears are those which match an externally toothed gear (generally denominated a rotor) with an internally toothed gear (generally denominated a stator) which surrounds and meshes with the former gear to provide relative rotation between the two gears. This rotational movement creates expanding and contracting fluid pockets between the teeth of the gears. If the device is being utilized as a motor, high pressure fluid is directed to the expanding fluid pockets, and if the device is being utilized as a pump, high pressure fluid is expelled from the contracting fluid pockets.

Since the spaces between the teeth alternately expand and contract in sequence around the periphery of the gears, valving means is required to direct the fluid to and from the fluid pockets in timed relation to the movement of the gears. Such valving means is oftimes denominated a commutator valve, and the valve is usually directly or indirectly connected to the gear members for synchronized movement and operation therewith.

Since both the rotor and the stator ring rotate on fixed axes at substantially diflerent speeds the axis of the rotor may be thought of, in a sense, as simultaneously orbiting about the axis of the stator ring but at a speed much different than the speed of rotation of the rotor. As a consequence of this speed differential, hydraulic devices employing gerotor gears find exceptional utility in a variety of applications in which torque is desirably increased with a corresponding reduction in speed, or in which speed is desirably increased with a commensurate reduction in torque.

Because of design problems inherent in the necessary co-operation between the gears and the commutator valve, however, hydraulic pumps or motors (the two terms can be considered synonymous herein since one is in the context there employed only the opposite of the other in terms of operation and function) which utilize gerotor gears have not enjoyed maximum usage where variation in pumping capacity or motor speed or torque is desired. Any means for varying volumetric capacity of the fluid pockets by varying the relative disposition or axial arrangement of the gerotor gears must take into account the indispensable requisite that the fluid be directed into and out of the fluid pockets in precise timed relation to the movement of the gears, and this necessarily raises difficulties concerning the manner of performing the commutation function by the commutator valve.

Furthermore, variable capacity positive displacement pumps or motors should desirably be adapted to operate with minimum fluid leakage for purposes of attaining high efficiency, and in considering such pumps or motors employing gerotor gears, the difficulties involved in minimizing leakage between the gear teeth of the rotor and stator where the two are adjustable relative to one another for purposes of varying volumetric capacity are indeed considerable.

To the solution of problems arising out of the provision of minimum leakage, variable capacity, positive displacement hydraulic pumps or motors utilizing gerotor gear members, the present invention is primarily addressed.

SUMMARY OF THE INVENTION The present invention may be summarized as involving a positive displacement hydraulic pump (or motor) utilizing a gerotor gear set having a pair of relatively rotatable (and, in a sense, orbital) gear members one of which surrounds the other in meshing relation for forming expanding and contracting fluid pockets between the teeth thereof and which utilizes roller vanes for forming the teeth thereof.

The pump (or motor) of the present invention may be of the variable capacity type and in one embodiment of the invention illustrated herein the gears of the gerotor gear set shift axially with respect to one another to vary the fluid confining volume of the pockets formed between the teeth of the gears. In another embodiment a second gerotor gear set is provided, the phase relationship of which may be varied with respect to the first to vary the effective displacement of the two gear sets.

In the embodiment in which the two gears of the gerotor gear set shift axially relative to one another to vary volumetric capacity the commutator valve, which directs the fluid into and out of the fluid pockets, also shifts axially. In the second embodiment the two gerotor gear sets are similar, the fluid pockets are crossported and the stators are axially aligned, but the rotors are adjustable relative to one another with respect to the axes of the stators so that the expanding and contracting fluid pockets of the two gear sets are brought into phase to increase effective displacement or out of phase to reduce effective displacement.

Among the objects of the present invention are to increase the applications of which hydraulic pumps or motors utilizing gerotor gear sets are susceptible, to increase the efficiency of variable capacity positive displacement hydraulic pumps or motors, and to provide means for varying the motor speed or pumping capacity of a gerotor gear pump or motor by internally varying the effective displacement of the gears.

Many other features, advantages and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description which follows and the accompanying sheets of drawings, in which preferred structural embodiments incorporating the principles of the present invention are shown by way of illustrative example only.

BRIEF DESCRIPTION OF THE DRAWING:

FIG. 1 is a cross-sectional view of a variable capacity positive displacement hydraulic pump or motor constructed in accordance with the principles of the present invention.

FIG. 26 are transverse sectional views taken respectively along lines II-II through VIVI of FIG. 1.

FIG. 7-is a partially sectioned view of another embodiment of the invention.

FIGS. 8-12 are transverse sectional views taken along lines VIIIVIII through XII-XII of FIG. 7.

FIG. 13 is a sectional view of a modified form of the invention disclosed in FIG. 7 which is of fixed capacity as opposed to the variable capacity of the embodiment shown in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1-6 there is disclosed a hydraulic motor or pump constructed in accordance with the principles of the present invention and indicated generally at reference numeral 10. As the description thereof proceedsit will become apparent that the invention has equal utility as a pump or as a motor and although the device 10 will be referred to hereinafter as -a motor, it should be understood that the term pump can be used interchangeably therewith in the context of the present invention.

The device 10 comprises a housing 11 having a bracket 12 through which extend a plurality of bores 13 to receive suitable mounting members such as threaded bolts or the like. Also formed in the housing 11 are a pair of openings 14 and 15 communicating respectively with threaded bores 16 and 17 for receiving complementarily threaded couplings for connecting to a pair of conduits conducting pressurized fluid to and from the device 10. Fluid opening 14 shall be referred to hereinafter as a fluid inlet opening and opening 15 as a fluid outlet opening, although it will be appreciated that the high and low pressure conduits can be reversed, the result of which is a reversal in the direction of rotation of the work output shaft of the motor 10 (work input shaft if the device 10 is being utilized as a pump).

That shaft is indicated at reference numeral 18 and is journalled in a pair of bearing and seal assemblies indicated respectively at 19 and 20. A key 21 is mounted on an outboard end 22 of the shaft 18 for coupling the shaft to a suitable work transmitting or absorbin member or device.

Formed within the housing 11 in axially spaced relation with respect to the axis of the work output shaft 18 are chambers 23, 24 and 25 formed respectively by cylinder walls 23a, 24a and 25a. The axes of the work output shaft 18 is offset with respect to the aligned axes of the chambers 23, 24 and 25 to the extent and in the manner indicated in FIG. 2, wherein the center line indicated at reference numeral 26 represents the center line of the shaft 18 and the center line indicated at 27 represents the center line of the chamber 24.

As shown in FIG. 1 a gerotor gear set including an externally toothed rotor 28 and an internally toothed stator ring 29 is disposed within the housing 11. The rotor 28, which rotates (and, in a sense, orbits) relative to the stator 29, is centrally apertured as at 30 to receive the work output shaft 18 and is connected for joint rotation to the shaft 18 by means of a key and keyway shown at 31. Thus, the rotor 28 rotates at the same time and at the same speed as the shaft 18.

Since the rotor 28 is mounted for joint rotation on the shaft 18, the axis thereof is also offset with respect to the cylindrical chamber wall 24a. To journal the rotor 28 within the cylinder wall 24a an axially aligned spacer 32 surrounds the rotor 28 and comprises a cylindrical outer wall 33 journalled in a bearing member 34 having an outer peripheral wall 36 the axis of which is aligned with the axis of the chamber wall 240 and an inner peripheral wall 37 the axis of which is aligned with the axis of the shaft 18 and of the rotor 28. Since the rotor 28 and the spacer 32 are separate and distinct parts it will be appreciated that the former can shift axially relative to the latter. The teeth of the rotor 28 are indicated at reference numerals 38 and the shaped complementarily to an inner wall 39 of the spacer, 32. As illustrated in FIG. 1, the axial dimension of the rotor 28, and thus the axial dimension of the teeth 38, is substantially greater than the axial dimension of thespacer 32 and the bearing member 34. In fact, in the embodiment of the invention illustrated in FIG. 1 the axial solvent of the rotor 28 is approximately twice the axial extent of the spacer 32. y

The external teeth 38 of the rotor 28 axially overlap the internal teeth of the stator ring 29 which, in the embodirnent illustrated, comprise a series of circumferentially spaced roller or tubular vanes 39 which are carried in recesses 40 formed in an inner peripheral wall 41 of the stator 29.

The walls on the recesses 40 are formed on a circular arc and extend slightly more than 180 around the vanes 39 to prevent removal of the latter radially from the former. The diameters of the recess walls 40 are, however, slightly greater than the diameters of the vanes 39 to enable the vanes to move both radially and circumferentially with respect to the axis of the stator 29 and to rotate within the recesses. As a consequence of this slight undersizing of the vanes 39 a hydrodynamically produced film of fluid exists between the vanes 39 and the recess walls 40 to prevent metal-tometal contact therebetween and to increase wear life.

The individual spaces between the stator vanes or teeth 39 and an outer wall 44 of the rotor 28 are indicated at reference numerals 43. The spaces 43, conveniently referred to hereinafter as fluid pockets, alternately and sequentially expand and contract as the gears 28 and 29 rotate in meshing relation with one another, and it is this expanding and contracting ability of the fluid pockets 43 which enables the device 10 to serve as a positive displacement pump or motor, as will be understood by those skilled in the art.

An outer wall 46 of the stator 29 is joumalled for rotation by the cylindrical wall 24a and is thus able to rotate relative to the housing 11. Disposed within the stator 29 in axially adjacent relation to the rotor 28 is a valve element 47 which is centrally apertured as at reference numeral 48 to accommodate the work input shaft 18. An outer peripheral wall 49 is notched or recessed as at 50 to accommodate the stator roller vanes 39 and consequently the valve element 47 and the stator 29 are interconnected for joint rotation.

A series of circumferentially spaced radially outwardly inclined fluid passages 51 are formed in the valve element 47 and extend between a pair of radial end walls 52 and 53. Passages 51 equal in number the number of fluid pockets 43 which in turn correspond in number to the stator vanes 39. One end 54 of each of the passages 51 communicates with a respective one of the fluid pockets 43 while an opposite end 56 communicates with a radial end wall 57 of another valve element 58.

The valve element 58 is disposed within the chamber 25 and is apertured as at 59 to accommodate the shaft 18. As shown in FIGS. 1 and 6, a pair of fluid passages 69 and 61 are formed in the valve element 58. Passage 61} is always located on one side of a line of eccentricity indicated at reference numeral 25 in FIG. 2, whereas passage 61 is located on an opposite side. As used herein the term line of eccentricity is defined as a line drawn transversely through the axes of the rotor 28 and the stator 29. Ends 62 and 63 of the passage 60 and 61 open to the radial end wall 57 of the valve element 58. An opposite end 64 of the passage 60 communicates with a circumferentially continuous passage 66 formed in the housing 11 in communication with the inlet opening 14. Passage 61 extends axially through the valve element 58 to an opposite end wall 67 and opens to a passage 68 which communicates with the fluid outlet 15.

Generally, the rotor member of a gerotor gear set has one less tooth than the stator member and in the illustrated embodiment the rotor 28 has teeth whereas the stator 29 has 1 1. It is in the nature of a gerotor gear set that as the'rotor is turned it will rotate about its own axis and orbit about the axis of the stator. As noted, this movement between the rotor and stator is only relative. Thus, the stator may be maintained stationarily and as the rotor is turned it will also orbit with respect to the axis of the stator. Conversely, the rotor may be maintained stationarily and as the stator is rotated it will also orbit relative to the axis of the rotor.

If n is the number of teeth of the rotor and n 1 represents the number of teeth of the stator, the relativeorbital speed between the rotor and stator (assuming one is actually permitted to orbit relative to the other) will equal the relative rotational speed times 1 divided by n.

In the illustrated embodiment the axes of both the rotor 28 and the stator 29 are maintained stationarily and in offset relation with respect to one another. To enable the rotor 28 and stator ring 29 to rotate relative to one another both must rotate relative to the housing 11. Since the rotor 28 has 10 teeth and the stator 29 has 1 1 teeth, the stator 29 will rotate only 10 times for each 1 l revolutions of the rotor 28.

The ability of the roller vanes 39 to rotate within the recesses 50, as a consequence of the slight undersizing thereof, tends to enhance the efficiency of the device 10 by reducing friction between the vanes 39 and the teeth 38 of the rotor 28 and reducing the torque required to rotate the stator ring 29 within the journal 24a. The hydrodynamic film of fluid formed between the outer walls of the vanes 39 and the recess walls 50 also tends to provide a more uniform application of the turning force around the circumference of the stator ring 29, thereby tending to more uniformly distribute and balance the bearing loads on the outer wall 46 of the stator ring 29 and increase wear life. Further, the roller vanes 39 enable the rotor 28 to be more easily shifted axially relative to the stator ring 29 for the purpose of varying the capacity of the device 10, as explained in greater detail hereinafter.

Since the valve element 47 rotates jointly with the stator 29 each of the passages 47 maintains constant communication with a corresponding fluid pocket 43. As the rotor 28 turns through one revolution and the stator 29 turns through 10/11 revolutions, each of the fluid pockets 43 expands and contracts between its maximum and minimum volumetric capacities. The expanding fluid pockets 43 all reside on one side of the line of eccentricity 25 (which intersects the axes of the rotor 28 and the stator 29) and the contracting pockets 43 reside on the opposite side of such line of eccentricity. The valve element 58 is maintained against rotation in the housing 11, and since the openings 62 and 63 of the axial fluid flow passages 60 and 61 formed therein each extend substantially half-way around the axis of the valve element 58, the expanding fluid pockets 43 constantly communicate with the high pressure fluid connected to the fluid inlet opening 14 and the con tracting fluid pockets 43 are in constant communication with the fluid outlet opening 15. Of course, when the device 10 is being utilized as a pump rather than a motor, the expanding pockets 43 communicate with the low pressure fluid whereas the contracting pockets communicate with the high pressure side of the pump as the rotor 28 and stator 29 rotate on fixed axes relative to one another and relative to the housing 1 1.

Since the valve elements 47 and 58 together perform the function of communicating the expanding and contracting fluid pockets 43 with high and low pressure fluid in timed relation to the movement of the gerotor gear members 28 and 29 they may be referred to as commutation valves, a denominative expression often employed by those skilled in the art in referring to valves of the same general nature.

The rate of flow of fluid through the device 10 depends, of course, on the speed of operation of the gear members 28 and 29 as well as on the volumetric capacities of the fluid pocket 43. Thus, by varying the volumetric capacity of fluid pockets 43, the flow rate of the device 10, if it is being used as a pump, can be varied without varying the speed of rotation of the shaft 18, and the speed of the shaft 18 can be varied, if the device 10 is being used as a motor, without varying the flow rate of the fluid flowing through the device 10.

The volumetric capacity of the fluid pocket 43 is varied, in the embodiment of the invention shown in FIGS. 1-6, by moving the rotor 28 axially with respect to the stator 29. Thus, as shown in FIG. 1, the bearing ring 34 (which is held against rotation by means of a pin 69), the spacer ring 32 and the stator ring 42 are sandwiched between a pair of radial walls 70 and 71 and are therefore unable to move axially. Rotor 28, however, is able to move leftwardly from the position thereof shown in FIG. 1. As the rotor 28 is moved leftwardly the volumetric capacity of the fluid pockets 43, which is greatest in the position of the rotor 28 shown in FIG. 1, is reduced accordantly with a corresponding reduction in axial overlapping of the teeth of the rotor 28 and the stator 29.

It is apparent that in order to maintain suitable commutation of fluid into and out of the fluid pockets 43 as the rotor 28 moves left-wardly, the valve elements 47 and 58 must also move leftwardly to maintain abutting engagement therebetween and between the valve element 47 and the rotor 28. Although the valve element 58 cannot rotate, axial movement thereof is permitted by means of an alignment shaft 72 which is carried in cooperating aligned bores 73 and 74 formed respectively in the valve element 58 and in the housing 11. The flow passages 66 and 68 which are formed in the housing 11 are constructed so as to maintain constant communication respectively with flow passages 60 and 61 formed in the valve element 58 regardless of axial movement of the valve element 58.

The rotor 28 is biased rightwardly to the position thereof shown in FIG. 1 by means of a helical spring 76, one end 77 of which is bottomed at the closed end of an annular recess formed in the housing 11, and an opposite end 78 of which is bottomed on a washer-79. The washer 79 is centrally apertured as at 80 to accommodate the shaft 18 and abuts a raised circumferential land 81 formed on the rotor 28. The outer diameter of the washer 79 is less than the diameter of the chamber wall 23a to permit axial movement of the washer within the chamber 23.

The rotor 28 (as well as the commutation valve elements 47 and 58) may be moved leftwardly against the bias of the spring 76 by any suitable means. In the embodiment illustrated the stud shaft 72 which prevents rotation of the valve element 58 serves as a piston member and the bore 74 in which his carried serves as a pressurized cylinder, one end of which communicates with a bore extension 82 adapted for communication to a suitable source of pressurized control fluid through an adjustable valve. Thus, the movement of the valve elements 47 and 48 and the rotor 28 (and thus the volumetric capacity of the device 10) can be selectively adjusted by means of a suitable hydraulic valve. It will be apparent, however, that mechanical means can also be provided for selective axial movement of the shaft 72.

It is noted that the rotor 28 can be moved leftwardly a sufficient distance such that the extent of overlapping of the teeth of the rotor 28 in the stator 29 is reduced to 0. In that event the flow capacity of the device 10, if

being used as a pump, is reduced to and the speed of the shaft 18, if the device is being used as a motor, is reduced to 0. The position of the rotor 28 in FIG. 1 represents the greatest volumetric capacity of the fluid pockets 28 and thus represents the relative disposition of parts when the speed or flow capacity of the device 10 is at its maximum condition.

FIGS. 8-12 represent another embodiment of the present invention. The operation of that embodiment, however, can perhaps best be described by making reference to the hydraulic device shown in FIG. 13.

This latter figure discloses a fixed capacity positive displacement hydraulic motor or pump utilizing a pair of gerotor gear members as the fluid displacement mechanism. The device, indicated generally at reference numeral 86, comprises a housing 87 which journals a work input/output shaft 88 which is coupled for joint rotation to a rotor gear member 89 disposed within a stator ring 90 which employs roller vanes 90a carried in oversized recesses to form the teeth thereof. A pair of fluid passages 91 and 92, which are similar to passages 60 and 61 shown in FIG. 6 of the earlier embodiment of the invention, open through a radial wall 93 of the housing 87 to the fluid pockets formed between the teeth of the rotor 89 and the stator 90. The rotor and stator are sandwiched between the radial wall 93 and an opposite wall 94 to prevent relative axial movement thereof. Thus the volumetric capacity of the fluid pockets formed between the teeth of the rotor 89 and the stator 90 cannot be varied.

The embodiment of the invention shown in FIGS. 7-12 comprises a pair of gerotor gear sets, the offset relation of the rotors of which are adjustable to vary the total effective volumetric capacity of the pockets formed between the teeth of the two rotors and their respective stators.

Accordingly, the device shown in FIGS. 7-12, indicated generally at reference numeral 96, comprises a housing 97 in which are formed a pair of fluid openings 98 and 99. A work input-output shaft 100 is journalled for rotation on a fixed axis within the housing 97 and has mounted thereon for joint rotation therewith an externally toothed rotor 101, which constitutes one of the two gears of a first gerotor gear set indicated generally at reference numeral 102. The internally toothed stator of the gear set 102 is shown at 103 in surrounding and meshing relation with the rotor 101.

A second gerotor gear set is shown generally at reference numeral 104 and comprises an externally toothed rotor 106 and an internally toothed stator 107. A, spacer plate 108 is disposed between the gerotor gear sets 102 and 104 and is connected for joint rotation to the stators 103 and 107 by means of a plurality of circumferentially spaced alignment pins 109. The stators 103 and 107 and the spacer plate 108 are journalled for joint rotation in a cylindrical wall 110 which forms the chamber within the housing 97 in which the gerotor gear sets 102 and 104 are disposed.

The fluid openings 98 and 99 formed in the housing 97 communicate respectively with a pair of fluid passages 111 and 112 which terminate at openings 111a and 1120 formed in a radial wall 113 which defines, along with an opposite radial wall 114 and the cylindrical wall 110, a gear chamber in which the gerotor gear sets 102 and 104 reside. The openings 111a and 112a each extend substantially halfway around the axis of the shaft 100 and the rotor 101. A series of expanding and contracting fluid pockets 116 are formed between the teeth of the rotor 101 and the stator ring 103. The fluid opening 111a communicates directly with those fluid pockets 116 which are disposed on one side of the line of eccentricity of the gerotor gear set 102 while the opening 1 12a openly communicates with the fluid pockets 116 located on the opposite side of the line of eccentricity.

A series of similar fluid pockets 117 are formed between the teeth of the rotor 106 and the stator 107 of the gerotor gear set 104 and since, in the embodiment illustrated in FIGS. 7-12, the gear members of the gerotor gear sets 102 and 104 are similar in size the fluid pockets 116 and 1 17 are sized identically.

The rotor 101 is coupled to the shaft 100 for joint rotation by means of a key and keyway arrangement indicated at reference numeral 118. Thus, as the rotor 101 is turned by virtue of the conducting of pressurized fluid to the fluid pockets 116 on one side of the line of eccentricity, the shaft 100 will turn at the same speed.

As shown in FIG. 9 the rotor 101 comprises a total of ten teeth, indicated at reference numerals 119. The internal teeth of the stator 103 are formed of roller vanes and are greater in number by one than the number of teeth 119 of the rotor 101. Thus, as the rotor 101 turns to one revolution the stator 103 will rotate through 10/ 11 revolutions.

The rotor 106 and the stator 107 of the second gerotor gear set 104 have the same number of teeth as do the rotor and stator of the first gerotor gear set 102.

Since the stator 107 is coupled to the stator 103 for joint rotation by means of the pins 109, the rotor 106 will be driven for rotation at the same speed as the rotor 101.

The rotor 106 is mounted for relative rotation on an eccentric extension 121 of an adjustment shaft 122 which is joumaled for rotation in the housing 97 on an axis which is aligned with the axes of the stator rings 103 and 107. A housing end cap 123 is mounted for joint rotation on a rear extension 124 of the shaft 122 and a manually actuated handle 126 is mounted thereon for selectively rotating the end cap 123 and thus the shaft 122. As shown in FIG. 7, a spherical ball lock 127 is carried in a cylindrical bore 128 formed in the end cap 123 and is biased by means of a spring member 129 into seating engagement with a circumferentially spaced series of recesses 130 formed in an end wall 131 of the housing 97. Thus, the shaft 122 can be selectively rotationally adjusted and spring-locked into position.

As the shaft 122 is rotated the eccentric shaft extension 121 causes the rotor 106 to shift orbitally with respect to the axis of the stator ring 107 and thereby angularly shift the line of eccentricity of the gerotor gear set 104.

For example, the line of eccentricity of gerotor gear set 102 is shown in FIG. 9 at reference numeral 125 as extending vertically as it intersects the axes of the rotor 101 and the stator 103. The shaft 122 can be adjusted so that the rotor 106 registers or is in axial alignment with the rotor 101, in which event the line of eccentricity of the gerotor gear set 104 also extends vertically and is aligned with that of gerotor gear set 102.

On the other hand, the shaft 122 can be rotated to cause the rotor 106 to move out of axial register with the rotor 101 to the position thereof shown, for example, in FIG. 11. The line of eccentricity of the gerotor gear set 104 in the relative disposition of the parts shown in FIG. 11 is at an angle from the vertical. In addition, the axis of the rotor 106 is below the axis of the stator ring 107, in contrast to the arrangement of gerotor gear set 102 in which, as shown in FIG. 9, the axis of the rotor 101 is above the axis of the stator ring 103.

As shown in FIG. 10, the spacer plate 108 has a plurality of radially angularly spaced apertures 132 extending axially therethrough and arranged in register with the fluid pockets 116 formed between the roller vanes or teeth 120 of the stator 103. As shown in FIG. 7, the apertures 132 extend radially outwardly beyond the teeth 119 of the rotor 101 and therefore all are in communication with their corresponding openings 111a and 112a ofthe fluid passages 111 and 112 via the fluid pockets 116.

In describing the operation of the device 96, assume in the first instance that the shaft 122 is rotated so that the rotor 106 of the gerotor gear set 104 is brought into axial register with the rotor 101 of the gerotor gear set 102. Further assume that the source of high pressure fluid is connected to the fluid opening 98 so that the fluid pockets 116 which communicate with passage 111 on one side of the line of eccentricity of the gerotor gear set 102 are subjected to high pressure fluid and the fluid pockets 116 on the opposite side of the line of eccentricity communicate with the fluid passage 116 and thence the fluid opening 99.

Since the rotor 106 is in direct axial register with the rotor 101, fluid pockets 117 formed between the teeth of stator 107 communicate respectively with the same fluid passage 111 or 112 as their direct counterparts 116. Thus, all of the fluid which flows from fluid inlet opening 98 to the fluid outlet opening 99 must move within one of the fluid pockets 116 on one side of the line of eccentricity of the gerotor gear set 102 to the other side of the line of eccentricity. Thus, each unit of volume of fluid, in passing through the gerotor gear set 102, performs an operating function in rotating the rotor 101 and thus the shaft 100. v

Now assume that the shaft 122 is rotated to a position whereby the rotor 106 is in the position thereof shown in FIG. 11. Since rotor 106 is no longer in axial registry with rotor 101, the line of eccentricity of the gerotor gear set 104 is angularly disposed with respect to the line of eccentricity of the gerotor gear set 102.

When the rotor 106 is not aligned with rotor 101, the high pressure fluid which enters one or more of the fluid pockets 116 (which number depends upon the degree of misalignment of the rotors 101 and 106) may be short circuited through their corresponding apertures 132 formed in the spacer plate 108 and fluid pockets 1 17 formed between the teeth of the stator 107 to flow to the fluid outlet passageway 112 in an unconfined manner and without performing a work output function insofar as rotation of the rotor 101 and of the shaft is concerned.

In fact, it is possible for the shaft 122 to be rotated such that the rotor 106 is exactly out of phase with the rotor 101, the position thereof which almost obtains in FIG. 11. When this complete out-of-phase relationship exists between the rotors 106 and 101 all of the fluid may be short circuited through the gerotor gear set 102, the spacer plate 108 and the gerotor gear set 104 without performing any useful work.

Consequently, if the device 96 is being utilized as a motor, the speed of the shaft 100 may be varied without varying the rate of pressurized fluid through the device. On the other hand, if the device 96 is being used as a pump the capacity thereof may be varied without varying the speed of shaft 100.

Although minor modifications may be suggested by those skilled in the art, it should be understood that we wish to embody within the scope of the patent warranted hereon all modifications as reasonably come within the scope of our contribution to the art.

What we claim is:

1. A variable displacement hydraulic pump comprismg a housing having a fluid inlet and a fluid outlet,

a shaft rotatably mounted on said housing,

a pair of gear members carried within said housing for relative orbital and rotational movement about a central axis and having gear teeth axially overlapping one another in meshing relation to provide expanding and contracting fluid pockets therebetween,

means rotationally interconnecting one of said gear members and said shaft, and

commutation means for communicating said fluid inlet and said fluid outlet with said fluid pockets in timed relation to the relative orbital and rotational movement of said gear members,

said gear members being movable axially relative 2. The invention as defined in claim 1 wherein said to one another to vary the degree of overlapping commutator valve assembly comprises a pair of valve of Said gear teeth and the fluid confining volume elements one of which is carried for rotation about said of the pockets therebetween, central axis and the other of which is maintained rotasaid commutation means comprising a commuta- 5 Q Y,

tor valve assembly disposed axially adjacent said both of Said elements bemg movable axially gear members d bl i ll therewith f accordance with the relative axial movement of directing fluid into and out of said fluid pockets gear membersin an axial direction. 

1. A variable displacement hydraulic pump comprising a housing having a fluid inlet and a fluid outlet, a shaft rotatably mounted on said housing, a pair of gear members carried within said housing for relative orbital and rotational movement about a central axis and having gear teeth axially overlapping one another in meshing relation to provide expanding and contracting fluid pockets therebetween, means rotationally interconnecting one of said gear members and said shaft, and commutation means for communicating said fluid inlet and said fluid outlet with said fluid pockets in timed relation to the relative orbital and rotational movement of said gear members, said gear members being movable axially relative to one another to vary the degree of overlapping of said gear teeth and the fluid confining volume of the pockets therebetween, said commutation means comprising a commutator valve assembly disposed axially adjacent said gear members and movable axially therewith for directing fluid into and out of said fluid pockets in an axial direction.
 2. The invention as defined in claim 1 wherein said commutator valve assembly comprises a pair of valve elements one of which is carried for rotation about said central axis and the other of which is maintained rotationally stationary, both of said valve elements being movable axially in accordance with the relative axial movement of said gear members. 